APPARATUS FOR GLUING OF VENEER SHEETS

DISPOSITIF DE COLLAGE DE PLACAGES

English Abstract

Apparatus for applying glue to veneer sheets comprises elements (6, 7, 8) for transporting veneer sheets (3), supported substantially in a horizontal position, to the gluing, a glue applying device (2) for administering glue onto the veneer traveling under it, as well as elements (9,10, 11) for directing the glued veneers (4), supported substantially in a horizontal position, to a further processing, said conveying elements being located with respect to each other so as to leave in the direction of transport a transfer gap aligned with the glue administering device (2). The device further includes means for forcing the veneer to be glued and the glued veneer at its center portion in the direction of transport to a different level than the edge portions thereof in the direction of transport.

French Abstract

Dispositif de collage de placages comprenant les éléments (6, 7, 8) pour le transport des placages (3), soutenus en position horizontale, pour le collage, un dispositif d'application de colle (2) pour la pose de colle sur le placage qui se déplace sous l'appareil, ainsi que les éléments (9,10, 11) pour l'acheminement des placages collés, soutenus à l'horizontale, vers d'autres étapes de traitement; ces éléments de transport étant situés les uns par rapport aux autres de manière à laisser dans la voie d'acheminement un écart aligné avec le dispositif de collage (2). Le dispositif peut aussi forcer le placage à coller et le placage collé à sa position centrale dans le sens de déplacement vers un niveau différent que les rebords de celui-ci dans le sens du déplacement.

Claims

CLAIMS
1. An apparatus for applying glue on at least one veneer sheet, said apparatus
comprising:
elements for transporting a veneer sheet, supported substantially in a
horizontal position,
to gluing;
a glue-applying device for administering glue onto a veneer traveling under
it; and
elements for directing a veneer having the administered glue on its top
surface, supported
substantially in a horizontal position, to further processing,
wherein said transporting elements and said directing elements are located
with respect to
each other so as to leave in the direction of transport a transfer gap aligned
with the glue-
applying device, and wherein said apparatus comprises means for forcing each
of the veneer to
be glued, lying on the transporting elements, and the glued veneer, lying on
the directing
elements, to a different level at its center portion in the direction of
transport than its edge
portions in the direction of transport.
2. The apparatus according to claim 1, wherein:
the transporting elements and the directing elements comprise belt conveyors,
belt conveyors at the central portion of the veneer in the direction of
transport are located
on a different level than belt conveyors supporting the edge portions of the
veneer, and
the belt conveyors in a lower level are suction belt conveyors.
3. The apparatus according to claim 1 or 2, wherein each directing element
supporting the glued veneer is located on a lower level with respect to the
corresponding
transporting element supporting the respective veneer to be glued.
4. The apparatus according to any one of claims 1-3, wherein the location of
the
transfer gap between the gluing point of the transporting elements and their
corresponding
directing elements is staggered with respect to the respective transfer gap of
an adjacent
conveyor element pair, and wherein the glue-applying device has two parts
corresponding to the
staggering.
6

5. The apparatus according to claim 2, wherein the transporting surface of
each belt
conveyor is rotated around an axis parallel with the direction of transport,
with different degrees
at different points along the length of the conveyor.
7

Description

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Apparatus for gluing of veneer sheets
The present invention concerns an apparatus for applying glue onto wood veneer
sheets for
example in order to j oint the veneers for producing plywood panels. The basic
construction of
this apparatus comprises conveyor elements, on which the veneers are supported
when being
conveyed substantially on a horizontal plane through the gluing apparatus. The
glue is applied
to the upper surface of the veneers by running it from a gluing device. The
gluing device
extends over the veneers in a direction across the proceeding direction of the
veneers, and has a
row of nozzles on its lower surface for running glue with a predetermined
dosage.
Traditionally the glue is run foamed.
A problem with this kind of apparatus is that parts of the apparatus easily
become tacky. Some
of the glue inevitably ends up to the parts of the apparatus, from where it
wanders to such
veneer surfaces where it is not intended. The glue on a wrong surface causes
problems in the
later phases of the production. The most problematic point in the gluing
device has appeared to
be the place where the gluing device itself is situated. The veneer has in its
proceeding
direction a certain dimension when it reaches the gluing point. Usually this
dimension is
produced in a preceding cutting phase. In practice a gap remains between the
successively
proceeding veneers, which gap must be taken into account when controlling the
administration
of glue The gap is typically about 50 mm wide, ranging from 0 to 3000 mm. The
administration is controlled based on monitoring the proceeding of the
veneers, and by starting
and stopping the administration, if a gap between the veneers is wider than
usual. Short gaps
between veneers, instead, do not give rise to cut off the administration. An
exception, of
course, is the face veneer, where the cutting off must be exactly in
conformity with the length
of the veneer (no glue allowed on the upper surface). The control of the
administration,
however is not able to eliminate totally the inaccuracy of the administration,
like dripping of
the glue from the nozzles after cut-off. Therefore the conveyors transporting
the veneer have
been arranged in the apparatus into two groups, firstly to conveyors for
bringing the veneers to
the gluing and secondly to conveyors for bringing the glued veneer forward
from the glue
administering device. Between these conveyor groups there has been left an
open space across
the transport direction at he point where the glue administering device is
situated. Thus, the
glue dripping eventually when the gap between the successive veneers is below
the glue
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administering device, is free to drip into a suitable receiver arranged below
the gap. Holes
eventually existing in a veneer causing the glue to penetrate are not able to
cause problems in
this arrangement either. One problem, however, arises, how to guide the veneer
to pass over
the empty distance inevitably remaining between the transports below the glue
administering
device.
An improvement for this controlling problem is provided in accordance with the
present
invention. At the same time, the behavior of the veneer in the gluing
apparatus has been
substantially improved, also in other respects. This is achieved by providing
the veneer
transporting apparatuses with means to bend a veneer sheet across its
traveling direction both
before and after the glue administering device so that the middle area is
positioned on a level
different from the mutual level of the traveling direction edge areas.
Thus, a flexural stiffness is achieved to a veneer sheet in the gluing
apparatus, in other words,
the veneer will be bent to an arc in the direction across the direction of
traveling.
The invention will be described in more detail in the following, with respect
to the enclosed
drawing, wherein
Figure 1 shows a schematic view of a gluing apparatus in accordance with the
present
invention,
Figure 2 shows the principal construction of the apparatus of Figure 1,
Figure 3 shows an alternative embodiment of the construction of the apparatus
in
accordance with the invention, and
Figure 4 shows an alternative embodiment of the apparatus in accordance with
the
invention for the part of the gluing device.
Figure 1 shows a gluing apparatus, wherein glue is dispensed onto a veneer
sheet 3 coming to
the apparatus, when said veneer sheet travels under a glue administering
device 2. The glue is
distributed to the veneer from the parallel nozzles of the device 2 as glue
stripes 1. The amount
of glue for each stripe is administered so that in the following processing
phases, where the
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glued veneer sheet is pressed together with another veneer placed onto it, the
glue is spread to
cover the whole surface of the veneer sheet.
The arrangement of the devices transporting the veneer supported on the gluing
apparatus is
illustrated in Figure 2. The conveyors 6, 7, 8 bring the veneer under the glue
administering
device (device 2 in Fig.l) and conveyors 9, 10, 11, respectively, bring the
glued veneer
forward to the further processing. The conveyors for taking in the veneer are
substantially
located aligned with the respective conveyors for taking out the veneer,
however so that there
is a transfer gap left between the conveyors in the direction of transport.
The glue
administering device is placed above this transfer gap. At the transfer gap
there is a free fall for
the glue eventually dripping between the successive veneer sheets to a
receiver located below,
and it will not be in touch with such parts of the apparatus, that could move
glue to the surfaces
of the veneers to be processed.
The veneer coming to the gluing after a drying process is bend in different
directions, as is
well known, and it is difficult to direct it to travel controlled under the
glue administering
device, as well as to travel glued forward to the further processing. In
accordance with the
invention, the veneer is made significantly more braced in these processing
phases by forcing it
to bend to some extent in cross direction with respect to its direction of
transport. This is
provided in the apparatus shown in the figures by forcing the central portion
of the veneer in
the direction of transport to press to a lower level than the edge portions
thereof. This
arrangement is visualized in Figure 2.
The inward conveyors 6, 7, 8 located parallel, have been implemented so that
the conveyors 6,
8 supporting the edge portions of the veneer are belt conveyors located at the
same level with
each other, whereas the conveyor 7 between them, being in contact with the
central portion of
the veneer, is a suction belt conveyor located on a lower level. As a result
of the suction caused
by the conveyor 7, the central portion of the veneer is pressed so as to form
a trough. At the
same time, the veneer is substantially braced in its direction of transport,
whereby it is
significantly better supported to reach over the transfer gap to the outward
conveyors 9, 10, 11.
The veneer bent to trough in cross direction with respect to its direction of
transport is also
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realigned quite easily for the part of local distortions caused by the drying,
which for its part
facilitates the handling of the veneer.
From the point of view of the operation of the device it is favorable that
also the outward
conveyors 9, 10, 11 are implemented in the corresponding way as the inward
conveyors 6, 7, 8,
although it is suitable to locate the outward conveyors staggered on a lower
level with respect
to the inward conveyors. Through staggering, the veneer can be prevented from
colliding with
the outward conveyors after it has passed over the transfer gap. The
staggering can have a size
ranging at about 50 mm.
For the part of the inward conveyors, the bending of the veneer can also be
implemented by
means of a pressing member operating on top of a usual belt conveyor 7 located
in the middle.
On the glued side this arrangement if naturally not applicable due to
staining.
An alternative embodiment of the construction and operation of the device is
that the veneer is
made to bend upwards in the middle, whereby the inward conveyors 6 and 8 and
the outward
conveyors 9 and 11, respectively, are on a lower level than the conveyors 7
and 10, and
preferably implemented as suction conveyors. For the part of the conveyors 6
and 8 the
pressing member described above is also applicable.
Figure 2 illustrates one special feature of the embodiment of the invention,
where the
conveyors 6, 8 and 9, 11, respectively, supporting the edges of the veneer,
are implemented so
that their conveying surface is turned around a transport direction axis in
different degrees at
different points of the length of the conveyor. Thereby the best possible
support can be
provided for the veneer at the different points of its advance.
As shown in Figure 3, there can be a plurality of conveyors on the inward side
and outward
side, arranged parallel, for instance two parallel suction conveyors in the
middle. In the
embodiment of the figure, the conveyors have been located staggered in the
direction of
transport for an embodiment of the gluing device in accordance with Figure 4.
In this
embodiment, the gluing device is implemented in two parts, and the parts 2',
2" are inclined
imitating the bending of the veneer below, whereby the distribution distance
from the
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distribution device to the surface of the veneer can be made more coherent
across the total
width of the gluing device.
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Representative Drawing